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From: Maarten Lankhorst <dev@lankhorst.se>
To: intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org,
	Maarten Lankhorst <dev@lankhorst.se>,
	Uma Shankar <uma.shankar@intel.com>
Subject: [PATCH 07/10] drm/i915/display: Handle vlv dsi workaround in scanline_in_safe_range too
Date: Thu,  2 Jul 2026 09:21:50 +0200	[thread overview]
Message-ID: <20260702072154.171324-8-dev@lankhorst.se> (raw)
In-Reply-To: <20260702072154.171324-1-dev@lankhorst.se>

Now that we have a macro, might as well handle the VLV dsi workaround
too.

This makes the vblank evasion code slightly more deterministic, by not
looping with interrupts disabled.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
---
 drivers/gpu/drm/i915/display/intel_vblank.c | 36 ++++++++++-----------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_vblank.c b/drivers/gpu/drm/i915/display/intel_vblank.c
index ca08059e088ea..6f1fa952b5391 100644
--- a/drivers/gpu/drm/i915/display/intel_vblank.c
+++ b/drivers/gpu/drm/i915/display/intel_vblank.c
@@ -739,6 +739,24 @@ static bool scanline_in_safe_range(struct intel_vblank_evade_ctx *evade, int *sc
 	else
 		*scanline = __intel_get_crtc_scanline(evade->crtc);
 
+	/*
+	 * On VLV/CHV DSI the scanline counter would appear to
+	 * increment approx. 1/3 of a scanline before start of vblank.
+	 * The registers still get latched at start of vblank however.
+	 * This means we must not write any registers on the first
+	 * line of vblank (since not the whole line is actually in
+	 * vblank). And unfortunately we can't use the interrupt to
+	 * wait here since it will fire too soon. We could use the
+	 * frame start interrupt instead since it will fire after the
+	 * critical scanline, but that would require more changes
+	 * in the interrupt code. So for now we'll just do the nasty
+	 * thing and poll for the bad scanline to pass us by.
+	 *
+	 * FIXME figure out if BXT+ DSI suffers from this as well
+	 */
+	if (evade->need_vlv_dsi_wa && *scanline == evade->vblank_start)
+		return false;
+
 	return *scanline < evade->min || *scanline > evade->max;
 }
 
@@ -769,24 +787,6 @@ int intel_vblank_evade(struct intel_vblank_evade_ctx *evade)
 		local_irq_disable();
 	}
 
-	/*
-	 * On VLV/CHV DSI the scanline counter would appear to
-	 * increment approx. 1/3 of a scanline before start of vblank.
-	 * The registers still get latched at start of vblank however.
-	 * This means we must not write any registers on the first
-	 * line of vblank (since not the whole line is actually in
-	 * vblank). And unfortunately we can't use the interrupt to
-	 * wait here since it will fire too soon. We could use the
-	 * frame start interrupt instead since it will fire after the
-	 * critical scanline, but that would require more changes
-	 * in the interrupt code. So for now we'll just do the nasty
-	 * thing and poll for the bad scanline to pass us by.
-	 *
-	 * FIXME figure out if BXT+ DSI suffers from this as well
-	 */
-	while (evade->need_vlv_dsi_wa && scanline == evade->vblank_start)
-		scanline = intel_get_crtc_scanline(crtc);
-
 	return scanline;
 }
 
-- 
2.53.0


  parent reply	other threads:[~2026-07-02  7:21 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-02  7:21 [PATCH 00/10] drm/intel/display: Changes required to make vblank evasion PREEMPT_RT safe Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 01/10] drm/vblank_work: Add methods to schedule vblank_work in 2 stages Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 02/10] drm/vblank: Add a 2-stage version of drm_crtc_arm_vblank_event Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 03/10] drm/intel/display: Make intel_crtc_arm_vblank_event static Maarten Lankhorst
2026-07-10 14:20   ` Ville Syrjälä
2026-07-02  7:21 ` [PATCH 04/10] drm/intel/display: Convert vblank event handling to 2-stage arming Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 05/10] drm/i915/display: Move vblank put until after critical section Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 06/10] drm/i915/display: Remove locking from intel_vblank_evade " Maarten Lankhorst
2026-07-02  7:21 ` Maarten Lankhorst [this message]
2026-07-02  7:21 ` [PATCH 08/10] drm/i915: Use preempt_disable/enable_rt() where recommended Maarten Lankhorst
2026-07-02  7:21 ` [PATCH 09/10] drm/i915/display: Make get_vblank_counter use intel_de_read_fw() Maarten Lankhorst
2026-07-10 14:34   ` Ville Syrjälä
2026-07-02  7:21 ` [PATCH 10/10] drm/i915/display: Do not take uncore lock in i915_get_vblank_counter Maarten Lankhorst
2026-07-10 14:19   ` Ville Syrjälä
2026-07-02  7:56 ` ✗ CI.checkpatch: warning for drm/intel/display: Changes required to make vblank evasion PREEMPT_RT safe Patchwork
2026-07-02  7:58 ` ✓ CI.KUnit: success " Patchwork
2026-07-02  8:33 ` ✓ Xe.CI.BAT: " Patchwork
2026-07-03  2:09 ` ✗ Xe.CI.FULL: failure " Patchwork
2026-07-10 14:43 ` [PATCH 00/10] " Ville Syrjälä

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